Astrocytes play important roles in the development and maintenance of the CNS. To understand and manipulate astrocyte function, this project addresses transcriptional control of the astrocyte-specific gfa gene that encodes an intermediate filament protein. Using transfection of astrocytoma cells with reporter gene constructs, multiple segments have been identified within the gfa promoter and upstream regions; the segments interact to control its expression. Site-directed mutagenesis is being used to pinpoint the critical specific sequences within these segments. This will be followed by isolation and study of the regulatory proteins acting at these sites. The activity of reporter constructs is also being studied in transgenic mice. Several constructs have been successfully incorporated into mouse lines, and preliminary results indicate that they drive gene expression in the brain. Continuing work will determine if their activity is specific to the CNS, and if so, if it is restricted to astrocytes. These studies will determine if the regulatory regions identified using cultured cells behave similarly in the living animal, and may permit development of an astrocyte-specific expression system for studying the effects of various genes on astrocyte function.